Milk thistles' large, spiny, dark-green leaves have white marbling ... it's possible to remove these deep-rooted weeds by hand. Craig McManus, founder of McPlants and host of The Garden Question ...

The second is Scotch Thistle, and this noxious weed was native to Eurasia. The plant has broad, spiny edged leaves and can grow over 12 feet tall. Scotch Thistle will develop a reddish purple to ...